Umted States Patent [19]
`Evanicky et al.
`
`US005896119A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,896,119
`*Apr. 20, 1999
`
`[54] REMOVABLE BACKLIGHTING ASSEMBLY
`FOR FLAT PANEL DISPLAY SUBSYSTEM
`
`[75] Inventors: Daniel E Evanicky. San Jose; Leroy
`Bertrand Keely. Portola valley; Steven
`Siefm 3911mm’ all "f Calif-
`
`5,568,164 10/1996 Ogawa .................................. .. 345/145
`5,593,221
`1/ 1997 Evanicky e! 81' -
`353/122 -
`5,654,779
`8/1997 Nakayama et a1. ................... .. 345/905
`5,661,839
`8/1997 Whitehead .............................. .. 385/31
`5,688,035 11/1997 Kashlma et a1. ........................ .. 362/31
`FOREIGN PATENT DOCUMENTS
`
`[73] Assignee: Silicon Graphics, Inc.. Mountain View.
`Calif.
`
`1-316790 12/1989 Japan .............................. .. G09F 9/00
`4-149417 5/1992 Japan ......................... .. G03B 21/132
`
`[* ] Notice:
`
`This patent is subject to a terminal dis-
`claimen
`
`[21] Appl. No.: 08/495,213
`[22] Filed:
`Jun’ 27’ 1995
`[51] Int. Cl.6 ..................................................... .. G09G 3/36
`[52] U S C]
`345/87, 345/102_ 345,905,
`'
`'
`' """""""""""""" "
`’
`’ 353/122’
`,
`_
`[58] Flew of Search """"
`
`63735;
`_
`‘
`
`’
`
`’
`
`[56]
`
`5:206:673
`
`.
`References cued
`US. PATENT DOCUMENTS
`,
`;aifka: :1‘ a1‘ """""""""""" “
`4/1993 Kawahara e}
`:hdurase ct
`
`n"
`
`"m
`
`353/98
`
`5,333,073
`7/1994 Suzuki . . . . . . . . . .
`5,353,075 10/1994 comm at 31,
`5,381,309
`1/1995 Bomhardt . . . . . .
`5,394,303
`2/1995 Wamabe 6* al-
`5,404,135
`4/1995 vog?ley 9* 31
`i2;
`e‘ "1' '
`362/31
`5’485’354 $1996 Ciupite e't
`""" "
`. 385/27
`5,548Z670
`8/1996 Koike ...... ..
`5,550,657
`8/1996 Tanaka et al. .......................... .. 359/49
`
`. . . .. 349/59
`353/122
`. . . .. 362/31
`362/31
`353/122
`
`I Pri'f‘ary Examiner-Rich“? A~ Hlerp?
`Assistant Examiner—Franc1s Nguyen
`Attorney, Agent, or F inn-Wagner. Murabito & Hao
`[57]
`ABSTRACT
`A light distributing removable door assembly (and elements
`thereof) for a back'lit ?at Panel display subsystem Whcrein
`the subsystem is for direct viewing as a monitor and having
`overhead projection capability. The removable door assem
`bly provides for back-lighting via a light pipe for direct
`viewing when installed in the subassembly. When the door
`assembly is removed, the active matrix LCD is semi
`transparent and can be placed over the imaging screen
`(viewing side down) of an overhead projector such that the
`LCD color image can be thus projected. The lamps that
`provide the back-lighting remain within the display sub
`system when the door is removed and a unique optical
`coupling is P‘O‘dd“d b°tw°°n ‘he lamps and a light PiPe
`the door. A
`bi-directional
`extraction
`
`Pawn is ‘189d 011 a light PiP¢ of tha removable door to
`provide effective and uniform light distribution over the
`LCD image. A clamping mechanism is also described within
`the removable door for securing the layers used in the door
`assembly. The clamping mechanism allows a reduction in a
`size of a junction formed between the lighting units of the
`subsystem and the removable door assembly.
`
`13 Claims, 19 Drawing Sheets
`
`60 cool:
`
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`SMALLER
`
`LGD_000713
`
`LG Display Ex. 1016
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 1 of 19
`
`5,896,119
`
`FIG.1A
`
`LGD_000714
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 2 0f 19
`
`5,896,119
`
`FIG. 1 B
`
`LGD_000715
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 3 0f 19
`
`5,896,119
`
`E
`
`u
`
`[10
`
`L
`
`LGD_000716
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`‘ Sheet 4 of 19
`
`5,896,119
`
`LGD_000717
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 5 of 19
`
`5,896,119
`
`LGD_000718
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 6 0f 19
`
`5,896,119
`
`\
`
`_
`
`45a
`
`FIGJIB
`
`LGD_000719
`
`

`

`US; Patent
`
`Apr. 20, 1999
`
`Sheet 7 0f 19
`
`5,896,119
`
`LGD_000720
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 8 of 19
`
`5,896,119
`
`LGD_000721
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 9 of 19
`
`5,896,119
`
`LGD_000722
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 10 of 19 9
`
`5,896,119
`
`Q3
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`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 11 of 19
`
`5,896,119
`
`360
`
`320
`
`325b
`
`370a
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`I
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`FIG_ 85 \X COOL AIR FLOW
`
`LGD_000724
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 12 0f 19
`
`5,896,119
`
`320
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`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 13 0f 19
`
`5,896,119
`
`410a
`
`20'
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`41Gb
`
`LGD_000726
`
`

`

`U.S; Patent
`
`Apr. 20, 1999 9
`
`Sheet 14 of 19
`
`5,896,119
`
`430
`435
`430
`435
`430
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`415b
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`
`LGD_000727
`
`

`

`US. Patent
`
`Apr. 20, 1999,
`
`Sheet 15 0f 19
`
`5,896,119
`
`10 \.
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`LGD_000728
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`

`

`U.S. Patent
`
`Apr. 20, 1999
`
`Sheet 16 0f 19
`
`5,896,119
`
`501 \
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`LGD_000729
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 17 of 19
`
`5,896,119
`
`259
`
`652
`
`OPEN
`
`REED
`SWITCH OPEN
`OH CLOSED
`?
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`CLOSED
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`V
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`654
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`TURN LAMPS
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`DATA FLOW
`TO BE LEFT
`TO RIGHT
`
`v
`I RETURN ’
`
`FIG. 12
`
`LGD_000730
`
`

`

`US. Patent
`
`Apr. 20, 1999
`
`Sheet 18 of 19
`
`5,896,119
`
`COLUMNICOLUMN COLUMN COLUMN
`1
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`
`LGD_000731
`
`

`

`U.S.' Patent
`
`Apr. 20, 1999
`
`Sheet 19 of 19
`
`5,896,119
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`

`

`5,896,119
`
`2
`
`1
`REMOVABLE BACKLIGHTING ASSEMBLY
`FOR FLAT PANEL DISPLAY SUBSYSTEM
`
`BACKGROUND OF THE INVENTION
`
`(1) Field of the Invention
`The present invention relates to the field of information
`display technology for electronic devices. Specifically. the
`present invention relates to a display component (and ele—
`ments thereof) capable of use within a computer system
`(2) Prior Art
`Flat panel displays or liquid crystal displays (LCDs) are
`popular display devices for conveying information gener-
`ated by a computer system. The decreased weight and size
`of a flat panel display greatly increases its versatility over a
`cathode ray tube (CRT) display. High quality flat panel
`displays are typically back-lit. That is. a source of illumi-
`nation is placed behind the LCD layers so that visualization
`of the resultant
`image is made much easier. However.
`providing a back-lit screen generally makes the display
`screen non-transparent. It is desired. then. to provide a LCD
`screen having the high quality image generation character-
`istics of a back—lit LCD. yet offering a transparent LCD
`screen. The present invention provides such advantageous
`capability.
`During meetings and lectures. overhead projection units
`or “projectors” are often used to project transparent slides.
`foils or “overhea
`” onto a screen or wall. The projection
`and resultant enlargement of these images onto the screen
`allows image presentation to a large audience. With the
`introduction of computer systems that ofier a wide range of
`software. including graphics packages and slide presentation
`capabilities. it would be advantageous to allow the graphic
`image output of a computer system to be projected and
`enlarged onto a screen for audience presentation. The
`present invention offers such advantageous capability.
`Further. some back-lit LCD screens utilize light extraction
`patterns. These screens have lamps along the edges of a light
`pipe and depend on an extraction pattern to distribute the
`light intensity. The light extraction patterns of the prior art
`are uni-directional in that the dots vary in size only in one
`direction. depending on their distance from the lamp in that
`dimension only. As a result. in prior art back-lit displays that
`utilize light extraction patterns. edges and comers are often
`darker and the overall image is not unifomrly bright. This
`condition requires that lights longer than the active area be
`used to account for the nonuniformity. It would be advan-
`tageous to provide acceptable uniform illumination of the
`LCD screen using lights of lower intensity (and shorter
`length) for power conservation. The present invention pro-
`vides such advantageous functionality.
`Accordingly. it is an object of the present invenn'on to
`improve the versatility of a flat panel display screen. It is an
`object of the present invention to provide an improved flat
`panel display screen that can be used with an overhead
`projector. It is also an object of the present invention to
`provide a direct view flat panel display screen that is back-lit
`that can also be used with an overhead projector to project
`and enlarge a resultant display image. It is yet an other object
`of the present invention to provide such capability in a
`portable computer system or a display subsystem wherein
`the back-lighting components of the display subsystem are
`removable. thus exposing a transparent LCD screen for use
`in combination with the overhead projector. It is yet another
`object of the present invention to provide a removable door
`assembly as discussed above wherein the illumination
`sources remain within the display subsystem unit when the
`
`LGD_000733
`
`back lighting door assembly is removed. These. and other
`objects of the present invention not specifically mentioned
`above. will become clearer within discussions of the present
`invention herein.
`
`SUMNIARY OF THE INVENTION
`
`10
`
`15
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`Alight distributing removable door assembly is described
`for a back-lit flat panel display subsystem wherein the
`subsystem is for direct viewing as a monitor and having
`overhead projection capability. The removable door assem-
`bly provides for back-lighting via a light pipe for direct
`viewing when installed in the subassembly. When the door
`assembly is removed.
`the active matrix LCD is semi-
`transparent and can be placed over the imaging screen
`(viewing side down) of an overhead projector such that the
`LCD color image can be thus projected. The lamps that
`provide the back-lighting remain within the display sub-
`system when the door is removed and a unique optical
`coupling is provided between the lamps and a light pipe
`within the door. A specialized bi-directional light extraction
`. pattern is used on a light pipe of the removable door to
`provide effective and uniform light distribution over the
`LCD image. A clamping mechanism is also described within
`the removable door for securing the layers used in the door
`assembly. The clamping mechanism allows a reduction in
`size of a junction formed between the lighting units of the
`subsystem and the removable door assembly.
`More specifically. embodiments of the present invention
`include a display subsystem for displaying video
`information.
`the display subsystem including: a display
`assembly for rendering the video information. the display
`assembly comprising: a flat panel display matrix having a
`first surface for viewing during direct monitoring and an
`opposite surface for viewing during overhead projection
`monitoring; a light source positioned along two opposite
`edges of the flat panel display matrix for providing back—
`light for the flat panel display matrix; and a removable door
`assembly. adapted for insertion into and removal from the
`display assembly. the removable door assembly comprising
`a light pipe for optically coupling with the light source to
`uniformly illuminate the flat panel matrix with the back-light
`when the removable door assembly is inserted into the
`display assembly and wherein the light source comprises a
`pair of light sets and wherein each light set comprises a pair
`of high voltage fluorescent tubes.
`The present invention also includes a bi-directional light
`extraction pattern of dots disposed on one surface of said
`light pipe for extracting light from said light pipe to illumi-
`nate said flat panel display matrix. each dot of said extrac-
`tion pattern varying in size depending on its position with
`respect to said light source along a first dimension and
`varying in size differently depending on its position with
`respect to said light source along a second dimension.
`Embodiments of the present invention also include a
`clamping mechanism having a minimized lip size and uti-
`lized to secure elements of the door assembly of the present
`invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1A is a perspective illustration of the front and side
`views of the display subsystem of the present invention with
`the direct viewing side facing outward and removal of the
`door assembly.
`FIG. 1B is a perspective illustration of the back and side
`views of the display subsystem of the present invention with
`the back side facing outward with the door removed.
`
`65
`
`LGD_000733
`
`

`

`5,896,119
`
`3
`FIG. 1C is a side view of the display subsystem in the flat
`extended position in the overhead projection orientation.
`FIG. 2 illustrates a perspective view of the removable
`door assembly of the present invention with the Viewing side
`facing outward.
`FIG. 3A is a perspective illustration of a lamp housing
`assembly used by the present invention.
`FIG. 3B is a cross—sectional view of a lamp housing
`assembly illustrating a shock mount and the lamps.
`FIG. 4 illustrates the display subsystem module with its
`direct viewing side down and the door assembly removed to
`expose the lamp housings and with the plastic case removed
`to expose internal structural support.
`FIG. 5 is a perspective illustration of the components of
`a lamp housing and its reflective tape and metal EMI shield.
`FIG. 6 illustrates the component layers of the removable
`door assembly of the present invention.
`FIG. 7 is a cross—sectional
`illustration of the optical
`interface between the lamp housing and the removable door
`assembly of the present invention.
`FIG. 8A is a perspective illustration of the display sub-
`system used in a configuration with an overhead projection
`unit of the present invention
`FIG 8B is a plane view of the top of the overhead
`projection unit of one embodiment of the present invention
`illustrating cooling air flow.
`FIG. 8C is a side view of the overhead projection unit and
`the display subsystem thereon to illustrate the aspects of the
`present invention that address the effects of the collumnation
`angle.
`FIG. 9A illustrates the back-lit LCD of the present inven-
`tion including the active matrix and the removable door
`assembly.
`FIG. 9B is an illustration of the anti-reflective conductive
`layers applied within the LCD of the present invention for
`emissions reduction.
`
`FIG. 9C is a logical block diagram of the anti-reflective
`conductive layers of the present invention.
`FIG. 10 is a logical block diagram of components of the
`present invention display subsystem.
`FIG. 11 is a logical blockdiagram of the image data fill
`and reversal components of the present invention display
`subsystem.
`
`FIG. 12 is a flow diagram illustrating process steps
`performed by the present invention upon insertion and
`removal of the door assembly.
`FIG. 13A illustrates forward (e.g.. left to right) data fill for
`image generation used in direct viewing of the display
`subsystem of the present invention.
`
`FIG. 13B illustrates reverse (e.g. right to left) data fill for
`image generation usedin overhead projection viewing of the
`display subsystem of the present invention.
`FIG. 14 illustrates a bi-directional light extraction pattern
`utilized by the present invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`In the following detailed description of the present inven-
`tion numerous specific details are set forth in order to
`provide a thorough understanding of the present invention.
`However. it will be obvious to one skilled in the art that the
`present invention may be practiced without these specific
`details. In other instances well-known methods. procedures.
`
`65
`
`4
`components, and circuits have not been described in detail
`as not to unnecessarily obscure the present invention.
`The present invention includes embodiments directed at
`an improved flat panel display subsystem that can be
`adapted for integration with or within a computer system.
`The high resolution color flat panel display has a back]
`lighting door assembly (“back-lighting assembly”) for direct
`viewing. This door assembly can be removed to expose the
`transparent active LCD display screen.
`Once removed. the transparent active LCD display screen
`can be positioned on top of an overhead projector in order
`- to project the displayed image in an enlarged fashion onto a
`receiving screen.
`With reference to FIG. 1A. a perspective view of the
`display subsystem of the present invention is illustrated with
`the display side facing outward This is the direct viewing
`configuration. Direction arrow 20' indicates the viewing
`direction. Light enters along “A” for projection viewing and
`along “B” for direct viewing. The display subsystem com-
`prises three major assemblies. The base assembly 12 which
`is coupled to a display assembly 10 via a hinge in order to
`allow the display assembly 10 to adjust to difierent angles
`for direct monitoring or allows the display assembly to lay
`flat for overhead projection configurations and for storage
`and transportation (as will be shown in FIG. 1C). The base
`assembly 12 supports the display 10 for direct viewing
`configurations and also contains several electronic circuit
`systems for providing the display unit with power. audio
`information, and video information. _
`The display assembly 10 contains two stereo speakers 8a
`and 8b as well as an active matrix LCD color screen 20.
`Although many difierent resolutions can be utilized within
`the scope of the present invention, an embodiment of the
`present invention utilizes an LCD screen 20 having 1024
`pixels by 768 pixels by RGB color and utilizes amorphous
`silicon thin film transistors ('I'FI‘). The LCD screen 20 is
`composed of color 'I'FF—LCD panel, drivm’ ICs. control
`circuitry. and power supply circuitry all contained in a rigid
`bezel. LCD screen 20 is capable of displaying 4096 true
`colors without frame rate modulation in text or graphics
`mode. An exemplary LCD screen 20 can be obtained by
`Mitsubishi Electronics as part number AA 12XA4D-NDES,
`however, various flat panel LCD screens and screen tech-
`nologies can be used within the scope of the present inven—
`tion with proper configuration.
`As shown in FIG. 1A. the display assembly 10 is back-lit
`via a separate assembly or removable door assembly 14. In
`this view the door is partially removed from the display
`assembly 10. The door assembly 14 is removed so that the
`display 20 can become transparent for overhead projection
`configurations. While inserted, the door assembly 14 pro-
`vides back-lighting for the LCD screen 20 for direct viewing
`configurations. Although a number of lamps can be utilized.
`one embodiment utilizes four cold cathode fluorescent
`(CCF) tubes which are located within the display assembly
`10 to illuminate along the top and bottom edges of a light
`pipe located within the door assembly 14 (as will be dis-
`cussed further below) when the door assembly 14 is inserted
`within the display assembly 10. It is appreciated that the
`high voltage CCF tubes are not removed from the display
`assembly 10 when the door assembly 14 is removed as to not
`break the high voltage connection that supplies power to the
`CCF tubes. Also shown is a snap fit clip 34 which is used to
`secure the door assembly 14 to the display assembly 10.
`FIG. 1 B illustrates the back side of the display subsystem
`(e.g.. along “B”) with the door assembly 14 completely
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`removed to expose inner components of the display assem-
`bly 10. In this View. with the door assembly 14 removed. the
`back side of the LCD screen 20 is exposed. Located on the
`base assembly 12 are inputs for AC power 44 and an
`audio/video input connector 48.
`Power supplied to the subsystem. backlight brightness
`and audio volume are controlled by the computer system’s
`software through the audio/video input connector 48. In an
`alternative embodiment. in addition to computer control
`these features can be manually adjusted. For instance. also
`located on the display subsystem can be (optionally) a power
`on switch 2a. a brightness adjustment knob 2b and a volume
`adjustment knob 20 for the stereo speakers 80 and 8b. The
`audio/Video input connector 48 is coupled to the digital
`audio/video output of a computer system. Under one
`embodiment of the present invention. the computer system
`is capable of transmitting (UNlX) compatible digital audio/
`video output signals.
`Located within the display assembly 10 are two lamp
`assemblies or housings. One lamp housing 40 is shown.
`Each lamp housing contains a pair of CCF lamps 52. There
`is a pair. as shown. on the bottom of the display assembly in
`lamp housing 40 and also a pair (obscured) of lamps on the
`top edge. Each pair of CCF lamps is mounted within its
`respective lamp housing using two rubber shock mounts. as
`shown. 50a and 50b to secure lamps 52. An identical
`configuration is employed for the top lamp housing
`(obscured). A reflective film 42 is applied to the inner
`portions of the lamp housings and this tape extends outside.
`beyond the positions of the lamps 52. for providing an
`optical coupling with components of the door assembly 14
`when inserted. The same is true for the upper lamp housing.
`Also shown in FIG. 1B are two receiving holes 32 located
`on the right and left sides of the display assembly 10. These
`receiving holes 32 fasten to corresponding latches (34 not
`shown) located on the door assembly 14. There is also a
`recess associated with these latch holes 32 for removal of the
`door assembly 14. Also located within this region of the
`display assembly 10 is a magnetic reed switch 22 that is
`responsive to the presence of a magnet 140 (not shown) that
`is located along the mating edge of the door assembly 14.
`Using this switch 22. the display subsystem determines
`whether or not the door assembly 14 is inserted or removed
`from the display assembly 10 and responds accordingly.
`It is appreciated that the reed switch 22 and sensor. in lieu
`of being magnetically operated. can also be implemented
`using and optical sensor (or switch. such as using a LED or
`fiber-optic device) or a mechanical sensor (or switch. such as
`a toggle or spring switch).
`There are also two notches 950 and 95b located on the top
`of the display assembly 10. These notches 95a and 95b are
`for mating with corresponding latches located on an over—
`head projector of the present invention for securing the
`display subsystem properly over an illuminating screen of
`the projector. When used in a projector configuration. the
`display subsystem is extended so that the base assembly 12
`and the display assembly 10 are flat and the facing side of
`the display subsystem. as shown in FIG. 1B. is placed facing
`down on top of the illuminating screen of the projector. In
`this way. light is projected through the back side of the LCD
`screen 20.
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`FIG. 1C illustrates the present invention display sub—
`system in its fiat configuration for storage or for use with an
`overhead projector. The base assembly 12 and the display
`assembly 10 are extended within a similar spatial plane.
`Alternatively.
`the base can be folded down toward the
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`overhead projector for added stability as shown. As shown
`by direction 20', the viewing side of the LCD screen is
`facing downward. This is the overhead projection configu-
`ration. The back side 14 of the display assembly (e.g.. where
`the door assembly 12 is inserted) is facing upward.
`Therefore. light passes through the LCD screen 20 in one
`direction for direct viewing (e.g.. back-lit viewing) and
`through the opposite direction when used for overhead
`projection. This is done. as will be explained further below.
`because the transistor layers of the LCD screen 20 are
`exposed at the rear end 14 and illumination energy from the
`overhead projector could cause them to malfunction or
`become destroyed if illuminated from the rear 14. Also at
`issue are considerations having to do with the collumnation
`angle of the light coming from the overhead projector. This
`is covered further below with respect to FIG. 8C.
`FIG. 2 illustrates a corner view of a fully assembled door
`assembly 14 of the present invention. The facing side 68 of
`the door assembly 14. as shown. is inserted into the display
`assembly 10. In the configuration as shown in FIG. 2. the left
`illustrated side of the door assembly 14 is inserted at the top
`of the display assembly 10. The door assembly 14 consists
`of a rigid back material 70 (in one embodiment is rigid
`plastic) upon which is mounted an acrylic light pipe 56
`which is planar having approximate dimensions to illumi-
`nate the LCD display screen 20 and is approximately 5—6
`mm thick in one embodiment. As shown in FIG. 2. the light
`housings located on the top and bottom of the display
`assembly 10 mate with the left and right sides of the door
`assembly 14 (in the orientation of FIG. 2). The light pipe 56
`distributes light from these edges throughout the active area
`of the LCD display 20 to illuminate the image. Located
`between the light pipe 56 and the back 70 is a rear reflector
`layer 120 (not shown in FIG. 2). Located on the surface of
`the light pipe 56 is a bi-directional light extraction pattern 60
`(to be described in more detail to follow).
`Placed on top of the light pipe 56 are several textured film
`layers 58 that are used to increase the intensity of light that
`is seen by a viewer through the LCD screen 20 and to
`provide other functions as will be described. The layers 58
`and the light pipe 56 and other components as described
`above are mounted to the door back 70 with a pair of clamps
`38a and 38b that each have a very small
`lip 64
`(approximme 1—1.5 mm or less) for grabbing and holding
`the film and light pipe layers. The lip 64 is small because the
`gap between the opening in the display assembly 10 (that
`receives the door assembly 14) and the active display area of
`the LCD screen 20 is very small. The clamps 38a and 3817
`are fastened to the back 70 via two screws each. however. a
`variety of mounting techniques can be employed.
`Referring to FIG. 2. located behind one of the clamps
`(here shown as 38b) is positioned a magnet 140. The clamp
`38b is made from a non—magnetic metal as to not interfere
`with the interaction between the magnet 140 and the reed
`switch 22. When the door assembly 14 is inserted into the
`receiving hole of the display assembly 10. the magnet 140
`aligns with the reed switch 22 to indicate the position of the
`door assembly 14. Also located on the outside edge of each
`clamp 38a and 3817. are two latches 34 for mating with
`receiving holes 32 located on the top of the display assembly
`10. These holes 32 and clamps 38a and 38b secure the door
`assembly 14 to the display assembly 10. As shown. surface
`68 is inserted into the display assembly 10 for back-lighting.
`FIG. 6 illustrates the component layers that form the door
`assembly 14 in more detail. The back cover 70 is shown and
`the position of the magnet actuator 140 is shown mounted
`within the door back 70. Mounted along the top and bottom
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`edges of the door back 70 are two shutoff reflectors 110.
`These reflectors 110 are used in combination with the
`reflective film 42 of the lamp housings 40 to create an optical
`junction or interface between the light pipe 56 and the lamps
`52. Positioned in between the light pipe 56 and the back 70
`is a rear reflector layer 120 made from a polyester reflective
`(e.g.. white) material in one embodiment of the present
`invention. The purpose of this reflector is to reflect light that
`is extracted by the light extraction pattern 60 placed on the
`light pipe 56. The reflector 120 redirects all the light that is
`extracted to the rear and redirects it to the front of the
`display. Located on the edges of the light pipe 56 that do not
`mate with a lamp housing are two edge reflectors 130 and
`these are made. in one embodiment. from a polyester/silver
`material. These serve to redirect any light escaping to the
`edges back into the active area.
`The dot pattern 60 is a light extraction pattern applied on
`the surface of the light pipe 56 that faces the rear reflector
`110. This pattern. according to the present invention, is
`bi-directional in that the size of the light extractors varies in
`two dimensions to account for decreases in light intensity in
`both of these dimensions. This will be discussed in more
`detail with reference to FIG. 13. As shown in FIG. 6, the
`light extraction pattern can be an ultraviolet curable white
`screen printable material and is applied directly to the
`surface of the light pipe 56. As is known with light extraction
`patterns and light pipes. the extraction pattern functions to
`alter the angle of light traveling within the light pipe so that
`the light is scattered and will exit (e.g.. become extracted)
`from the light pipe rather than become reflected within the
`light pipe. Any light incident upon any inside surface of the
`light pipe will pass through that surface if its incident angle
`is less than the Brewster angle. If its incident angle is greater
`than the Brewstm' angle (approximately 42 degrees) it will
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`be reflected and remain within the light pipe to be rescatrered
`again by the extraction dot pattern. The two edges and the ,
`rear of the light pipe are reflectorized so as to allow the light
`to be extracted only to the front (viewer) surface. When the
`door assembly 14 is assembled and inserted into the display
`assembly 10.
`the minimum raw surface brightness is
`approximately 3700 Cd/mz.
`The layers 58 as described with respect to FIG. 2 are
`shown in more detail in FIG. 6. Placed on top of the light
`pipe 56 is an omni-directional light gain diffuser 580 for
`increasing the amount of light incident along the angle of a
`viewer and in one embodiment is manufactured from a
`polycarbonate material and is approximately 5—10 mils
`thick. On top of the light gain difiuser 58a is a difluser layer
`58b for diffusing the light This layer 58b in one embodiment
`of the present invention is composed of a polycarbonate
`material and is approximately 5 mils thick. Its surface is of
`a roughened texture to insure a non-wetting contact to the
`rear of the brightness enhancement film BEF (58c) film. On
`top of layer 58b is a brightness enhancement film BEF (58c)
`that is composed of a polycarbonate material and is approxi-
`mately 10 mils thick in one embodiment. Lastly. a BEF
`protector layer 58d is placed over the BEF layer 58c for
`protection of the layers underneath. especially the micron—
`sized peaks of the BEF rib structure (to protect the micron—
`sized tips of the BEF which are very fragile). In one
`embodiment. layer 58d is composed of a polycarbonate
`material and is approximately 20 mils thick.
`These layers as shown‘ in FIG. 6 are secured to the back
`70 via stainless steel “L” shaped clamps 38a and 38b which
`are screwed into place. It is appreciated that the lip 64 of
`each clamp is very thin (approximately l-—1.5 mm). When
`assembled. the top and bottom edges of the light pipe 56 of
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`the door assembly 14 are exposed for receiving light from
`the lamp housings 40 of the display assembly 10. The
`viewing direction 20' for direct monitoring is also shown in
`FIG. 6.
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`It is appreciated that the door assembly 14 does not
`contain the lamp housings 40. This feature of the door
`assembly 14 is advantageous